The present disclosure relates in general to the field of machining of an eye using pulsed laser radiation, and relates in particular to a technique for aligning a pulse firing pattern relative to an eye of a patient.
Methods for laser-assisted surgery on the human eye include many different types of surgery, and have the objective of improving vision, treating eye disease, or both. Conventional known types of surgery include, for example, laser-assisted in situ keratomileusis (LASIK), corneal transplantation (keratoplasty), intracorneal lenticule extraction, implantation of intracorneal ring segments, implantation of corneal inlays, and the like, to name only a few. In certain forms of laser-assisted ophthalmic surgery, it is necessary to make one or more incisions in the eye to be treated. Such incisions may be made in human eye tissue using ultrashort pulsed laser radiation, wherein a beam focus of the laser radiation is guided in time and space according to a pulse firing pattern, so that the radiation pulses arrive at the eye at appropriate locations for achieving a desired cutting geometry in the eye which is represented by the pulse firing pattern.
For the success of a surgical procedure, it must be ensured that each incision is made at the correct location in the tissue of the eye. The pulse firing pattern should therefore be defined with reference to the position of one or more eye features, which may be located at the time of the surgical procedure by means of suitable imaging technology. Examples of eye features include a pupil center, an iris structure, the limbus, and a sclera structure (such as a blood vessel) of the eye.
Conventional cutting laser systems which are used for making an incision in a human eye are typically equipped with a patient adapter (patient interface) which is used for immobilizing the eye to be treated opposite from an opening at which the laser radiation is output from the laser radiation system. This radiation output opening may be situated, for example, on an output side of a focusing objective of the laser system. The patient adapter includes an applanation plate or some other contact element that provides a contact surface for the eye. When the eye is pressed against the contact element and the outer surface of the eye fits closely against the contact surface of the contact element, the cornea of the eye undergoes deformation. When the patient adapter has, for example, an applanation plate with a planar contact surface, the cornea is deformed in a flattened state.